Author Topic: PC Engine GT - No Video or Backlight  (Read 1147 times)

Keith Courage

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Re: PC Engine GT - No Video or Backlight
« Reply #15 on: October 14, 2021, 10:01:51 PM »
If you can't find the problem, the system would still be a good candidate for a 3.5" LCD screen upgrade since the replacement screens have their own back lights.

WaldoX

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Re: PC Engine GT - No Video or Backlight
« Reply #16 on: October 15, 2021, 12:26:30 PM »
If you can't find the problem, the system would still be a good candidate for a 3.5" LCD screen upgrade since the replacement screens have their own back lights.

That was my take as well, and my 3.5 screen kit is on the way.  :-)

WaldoX

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Re: PC Engine GT - No Video or Backlight
« Reply #17 on: November 24, 2021, 05:44:05 PM »
Just wanted to update and say that my cheap chinese soldering iron has started falling apart, so I'm waiting for a new one before I attempt this screen mod.   :|

I will update this thread though once I get around to the mod.  I won't lie, this mod scares me quite a bit, it'll be some of the smallest work I've done yet.  Wish me luck!   :bonkthis:

WaldoX

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Re: PC Engine GT - No Video or Backlight
« Reply #18 on: December 24, 2021, 07:15:56 PM »
Okay Gents (and ladies?), I finally got to this screen mod and....... wait for it.....STILL DOESN'T WORK!!!   ](*,) ](*,) ](*,)   

Essentially it's the same as before: I can hear the game playing, but I get no video.  The screen does light up (new backlit lcd), but no picture of any kind, just a blue background.  If I haven't made any mistakes, then what does this mean?  Does it mean the 6260 is dead or malfunctioning?  Any advice to troubleshoot further is really appreciated.

I modded my LCD Board for 5V according to this video: Turbo Express LCD Screen Mod! Installation guide and demonstration.  I followed this video in general, but was using a different video board, so I followed Console5's instructions on connecting it up.

I tested everything for continuity, and checked for bridges.  I tested for 5V at the capacitor and the video board.  I tested the 5V connection on the back for the LCD.

P.S. I don't know what the potetiometer on the video board is for, but I did try turning it completely both ways while powered up.

Incoming Picture Tsunami!!! 

Pins to lift markedLifted and Connected (I noticed the wonky cap at this point; I had apparently "repaired" it in the past and the connection was loose.  I replaced it with another later on)

GroundedGrounded Alt View
Done. OverheadVideo Board

LCD Board w 5V modPin 20 Connection
Pin 26 and Nearby Cap Connections


Pin 26, 33 and 40 ConnectionsPin 33 and 40 ConnectionsMod Board Pin Connections
Mod Board 5V and CapMod Board Resistors
LCD Board Pin 1 5V ConnectionLCD Board VR 5V Connection

LCD Power and Ground Connections


« Last Edit: December 24, 2021, 08:47:52 PM by WaldoX »

Keith Courage

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Re: PC Engine GT - No Video or Backlight
« Reply #19 on: December 26, 2021, 12:50:19 AM »
Your Video board has the traces going to different places than what I'm used to doing. This is the circuit I use minus the extra 75ohm resistor on the output.

As you can see, all 4 signal pins should be connected together after passing through their resistors. On your board they are not doing that. Also, 3 of your signal pins(20,26,33) are going to a spot with no transistor installed.

I also have no idea why there is a Potentiometer on there nor do I see why there is an extra Ceramic cap on your video board.

Here is one built from scratch. 


Also, here is a wiring guide for the LCD. https://mega.nz/file/IMw2hLLL#v667H2EfnD1HEcMF45zp-sSw311BdsKM-JAZJJPRUtI
« Last Edit: December 27, 2021, 07:25:15 AM by Keith Courage »

WaldoX

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Re: PC Engine GT - No Video or Backlight
« Reply #20 on: December 27, 2021, 10:52:12 AM »
Hey, thanks so much for the reply! 

As you can see, all 4 signal pins should be connected together after passing through their resistors. On your board they are not doing that. Also, 3 of your signal pins(20,26,33) are going to a spot with no transistor installed.

I completely agree that this seems BONKERS.  I'm having a hard time believing that Console5 would be selling a faulty board, but this is so weird!  Here are their pictures for this board:

EDIT: I was taking another look at Console5's board, and it appears to me that all the resistors do connect together and run through the single transistor on the board.  It looks to me like the PCB has multiple paths running around, but only utilizes one of them.  I'm a total noob at this though...


I should be getting some variety packs of resistors in soon and can try building one like yours, or I also have these boards that I can try once I get those resistors in.





 :boom: Would you mind though, just for a moment, assuming that their board works?  If it works, and I didn't screw it up, what would this mean for the PCE GT?  Bad video chip?


Thanks again!

« Last Edit: December 27, 2021, 10:55:33 AM by WaldoX »

Keith Courage

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Re: PC Engine GT - No Video or Backlight
« Reply #21 on: December 27, 2021, 09:37:22 PM »
I've never seen a HU6260 chip produce absolute no video at all. If bad, the colors or graphics are generally just all messed up.

I'm not saying it couldn't happen where the chip is dead altogether and won't produce any picture whatsoever. I've just never come across one that has done that.



« Last Edit: December 27, 2021, 09:40:59 PM by Keith Courage »

WaldoX

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Re: PC Engine GT - No Video or Backlight
« Reply #22 on: December 27, 2021, 09:50:43 PM »
I've never seen a HU6260 chip produce absolute no video at all. If bad, the colors or graphics are generally just all messed up.

I'm not saying it couldn't happen where the chip is dead altogether and won't produce any picture whatsoever. I've just never come across one that has done that.

Well that good to hear, I'll keep my fingers crossed that there's still hope here.  I noticed your version of the video board doesn't use a transistor, any idea what the other boards need one for?  Just curious!  I'll try making a board like yours or using one of these others I have and get back to you.

Thanks again!

Keith Courage

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Re: PC Engine GT - No Video or Backlight
« Reply #23 on: December 28, 2021, 02:39:13 AM »
The 75ohm resistor is just to lower the Brightness slightly but I think that's mainly just needed for other transistors that amp the signal more. I've noticed that the 8050 transistor has the correct brightness without one and will be too dark with one.

WaldoX

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Re: PC Engine GT - No Video or Backlight
« Reply #24 on: December 29, 2021, 10:03:30 AM »
The 75ohm resistor is just to lower the Brightness slightly but I think that's mainly just needed for other transistors that amp the signal more. I've noticed that the 8050 transistor has the correct brightness without one and will be too dark with one.

Thanks for that extra advice!  I just ordered a handful of those transistors, along with some prototyping board.  In a couple of weeks when that comes in, hopefully my resistor bible will be here too, and I'll get back to work on this project.

Thanks again!  Happy New Year!   :)

WaldoX

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Re: PC Engine GT - No Video or Backlight
« Reply #25 on: January 20, 2022, 01:06:30 PM »
I have gotten all of the parts in for the AV boards, so I'm hoping to tackle this project again this weekend.  I have 2 options for my Composite AV Board, I can build one with your (Keith's) schematic on prototyping board, and/or I can populate one of the boards I ordered from OshPark.

The boards from OshPark include an additional AV hookup on the board for doing an AV Out mod.  Does anyone know of any guides on doing AV Out?  I'd love to know how to repurpose the com port for this, if that's possible?  I've tried searching these forums and the internet in general, but haven't been able to find any guides on this.   :'(

MasterofBiscuits

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Re: PC Engine GT - No Video or Backlight
« Reply #26 on: January 24, 2022, 06:30:30 AM »
I have gotten all of the parts in for the AV boards, so I'm hoping to tackle this project again this weekend.  I have 2 options for my Composite AV Board, I can build one with your (Keith's) schematic on prototyping board, and/or I can populate one of the boards I ordered from OshPark.

The boards from OshPark include an additional AV hookup on the board for doing an AV Out mod.  Does anyone know of any guides on doing AV Out?  I'd love to know how to repurpose the com port for this, if that's possible?  I've tried searching these forums and the internet in general, but haven't been able to find any guides on this.   :'(

I don't have a guide, but I have seen people add a composite contact to the headphone jack. It involves drilling a tiny hole through it and inserting a wire. Repurposing the com port might be easier since you could just add in a 4 conductor jack, or any other type of port you wanted. Since there's no definitive standard for 3.5mm av cables, I'd recommend buying the cable first then wiring your socket to match it.

WaldoX

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Re: PC Engine GT - No Video or Backlight
« Reply #27 on: January 24, 2022, 11:17:36 AM »
Thanks for the advice, it's much appreciated!

FWIW, I built the Osh Park board this weekend, then before installing it I was going over the PCEGT board looking for problems and doing basics like checking voltages, and I blew a fuse somehow  :-/   I had to order fuses, so the project is on hold again.   :roll:

« Last Edit: January 24, 2022, 11:20:34 AM by WaldoX »

Keith Courage

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Re: PC Engine GT - No Video or Backlight
« Reply #28 on: January 24, 2022, 05:23:04 PM »
I just re-purpose the comport Jack for video out and then just use the headphone jack for the audio instead of installing a new port. 

WaldoX

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Re: PC Engine GT - No Video or Backlight
« Reply #29 on: January 25, 2022, 09:39:03 AM »
That sounds like what I was looking for, and I think I can figure out the rest on my own, but honestly, if I can just get this thing working, I'd be so happy.